This publication reports the results of an evaluation of nuclear energy systems based on a closed nuclear fuel cycle with fast reactors (CNFC-FR). The study was carried out by an international group of experts from Canada, China, France, India, Japan, the Republic of Korea, the Russian Federation and Ukraine, using an assessment methodology developed by the International Project on Innovative Nuclear Reactors and Fuel Cycles (INPRO). The INPRO methodology takes a holistic approach to assess innovative nuclear energy systems in seven areas: economics, infrastructure, safety, waste management, environment, proliferation resistance and physical protection. The study concluded that all INPRO requirements for a sustainable nuclear energy system are fulfilled by the assessed CNFC-FR, except in the area of economics, where ongoing R&D programmes will provide further insights to bridge knowledge gaps. The full text of the study results is available on the accompanying CD-ROM.